Sinister business: Lefties have evolutionary boon

Feb 27, 2009
US President Barack Obama uses his left hand to sign a bill on February 4, 2009. In a study published on Friday, French evolutionary biologists offer an explanation: left-handedness, they say, has survived because it is so rare.

Under Darwinian pressure, genes that don't help the struggle to survive get squeezed out of the genetic code, leaving the ones that are fitter.

Given that the vast majority of humans are right-handed, why is it that left-handedness -- of which President Barack Obama is a proud practitioner -- is still around?

In a study published on Friday, French evolutionary biologists offer an explanation: left-handedness, they say, has survived because it is so rare.

In prehistoric times, a left-hander would gain the advantage of surprise in fighting against a right-hander, they say.

In addition, left-handers tend to be skilful with their right hand or even ambidextrous. Most right-handers greatly prefer their right paw, which is a disavantage in a situation that demands intermanual coordination.

The paper, headed by Violaine Llaurens of the Institution of Evolutionary Sciences in Montpellier, southern France, estimates that left-handers comprise between five and 25 percent of the population, with important geographical variations.

Although the genes for left-handedness are so far elusive, there is compelling evidence that it is heritable, the authors believe.

If both of your parents are left-handed, the chance that you too will be a southpaw is more than twice than if your parents are right-handed.

Developmental factors could also play a role in left-handedness, such as the exposure to hormones in the uterus.

There is some good news for lefties in the study, which reviews published research in lateralism.

Compared with their low numbers in the general population, lefties are relatively numerous among creative men; among children rated as having an IQ higher than 131; and among individuals who are good at music and maths.

"All these advantages may play a significant role in the social status of left-handers," it says. Some research suggests that left-handed men are better paid than right-handers.

Even though lefties are clear survivors, their condition also carries an evolutionary cost, the authors warn.

They point to statistical surveys that suggest right-handers generally live longer than left-handers, by a few months or even several years.

Why this is the case is unclear. It could be partly explained by the greater number of fatal accidents involving left-handed men grappling with industrial tools, machines and instruments designed for right-handers.

Left-handers also tend to have smaller body size, which is linked to less reproductive success, and they tend to be more numerous in the homosexual population than in the general population.

As homosexuals tend to have fewer children or no children at all, this means that the "lefty" genes are less likely to be passed on, which counts as an evolutionary disadvantage.

The study appears in Philosophical Transactions of the Royal Society B, a journal published by Britain's de-facto academy of sciences.

(c) 2009 AFP

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User comments : 10

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bmcghie
3.7 / 5 (3) Feb 27, 2009
"Left-handers also tend to have smaller body size, which is linked to less reproductive success..."

last I checked, 6'3" is not 'smaller.' Then again, I might just be an outlier.
CreepyD
3 / 5 (3) Feb 27, 2009
Is handedness proven to be genetic? Nurture seems more likely to me. I do some things left handed because I learnt them that way. Also some things right handed, again because I learnt it that way. I just happen to learn most things with the right hand, so became 'right handed'.
Velanarris
3.7 / 5 (3) Feb 27, 2009
"Left-handers also tend to have smaller body size, which is linked to less reproductive success..."

last I checked, 6'3" is not 'smaller.' Then again, I might just be an outlier.
No, I'm 6'7" and also a lefty. I don't think lefties tend to be smaller in size, at least I've never seen any evidence to that.

Perhaps the fact handed-ness has zero interaction with survival, and the reason why it's so rare is because society shunned it for centuries? Left handers have been called the devil's children, and had their hands beaten until they used their right hands.

Also the ambidexterity piece is irrelevant because the world didn't become left or right handed until some leader shunned lefties forcing them to become right hand capable.


As for the prehistoric times comment, research is starting to show prehistoric man wasn't too warlike as resources were bountiful compared to the number of people needing them. This made cooperation rather than confrontation the norm as it allowed for a larger hunting group, more successful endeavors, more manual labor for farming, and eventually civilization.
GrayMouser
1 / 5 (1) Feb 27, 2009
"Left-handers also tend to have smaller body size, which is linked to less reproductive success..."

last I checked, 6'3" is not 'smaller.' Then again, I might just be an outlier.

I'm 6'1" and 2 of my brothers (also lefties) are 6'2" and 6'3". The shortest one in the lot is my right-handed brother at 5'10"...
Velanarris
not rated yet Feb 27, 2009
"Left-handers also tend to have smaller body size, which is linked to less reproductive success..."

last I checked, 6'3" is not 'smaller.' Then again, I might just be an outlier.

I'm 6'1" and 2 of my brothers (also lefties) are 6'2" and 6'3". The shortest one in the lot is my right-handed brother at 5'10"...

Coincidentally, the smallest of the three among myself and my siblings is also the only right hander.
jonnyboy
1 / 5 (1) Feb 28, 2009
I made up better fiction than this so called science, stoned at the age of thirteen. A collection of observations is not science, it is just a collection of observations.
rubberman
1 / 5 (1) Mar 01, 2009
6'3 also lefty, two right handed brothers, 6'0 and 5'11. Of course I also have hyper mobile joints which most doctors beleive is detrimental to coordination yet I don't generally have issues when it comes to athletic practice.
HeRoze
5 / 5 (1) Mar 04, 2009
No need to get defensive. The article didn't say that all lefties are intelligent, short, homosexuals. Interestingly, none of the lefties are arguing against being more intelligent.
Velanarris
1 / 5 (1) Mar 04, 2009
No need to get defensive. The article didn't say that all lefties are intelligent, short, homosexuals. Interestingly, none of the lefties are arguing against being more intelligent.


Well here's your argument from a lefty, we're not more intelligent, we're more capable of absorbing information due to having to percieve things in both a left and right handed view. It's the same and more so with truely ambidexterous people. On average they are more capable at assimilation of new systems because they have to assimilate systems that are built for right handers while they are not right handed.
thales
not rated yet Mar 09, 2009
Let's just say it: lefties are as gods among us.